To manage domain DNS you have to access our clientarea, then click on Domains -> My Domains
Click on the domain you want to edit from the list
Then on the right sidebar click on "DNS management"
You will see a notification
If you edit the dns of your domain the system will set our default nameservers, if you do not set all the records correctly your domain will go offline since our default nameservers are different from your server's nameservers. If you wish to edit a configuration you may want to use the dns editor in cpanel.
If you bought the domain only, with no hosting you can ignore this message.
If you want to proceed click on the red button and you will see a screen from which you can manage your DNS
As soon as you make a modification from to the DNS settings the system will set our default nameservers:
and it will be necessary to wait a few hours for the modifications to take effect
For it domain it's necessary to edit the nameservers first using the ones mentioned above, then edit the domain DNS.